Inspection Procedure 21: A/C Compressor Relay System




OPERATION



  • When the A/C switch "ON" signal is input to the engine-ECU, the engine-ECU places the A/C compressor relay in the "ON" position. Accordingly, the battery voltage supplied to the A/C compressor operates the magnet clutch.

PROBABLE CAUSES



  • Failed A/C compressor relay
  • Failed A/C compressor assembly
  • Damaged harness (Open circuit between A/C compressor relay and condenser fan relay, A/C compressor relay and engine-ECU, A/C compressor relay and A/C compressor, and open circuit between A/C compressor relay and relay box)
  • Damaged connector (A/C compressor relay connector, A/C compressor connector, Engine-ECU connector)
  • Failed engine-ECU

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III data list

  • Refer to Data List Reference Table .

  1. Item 25: A/C switch
  2. Item 26: A/C load signal <Automatic A/C>
  3. Item 27: A/C relay

Q. Is the check result normal?
Go to Step 2 .
Check A/C system (Refer to GROUP 55A - Troubleshooting - Trouble Symptom Chart <manual A/C>, GROUP 55B - Troubleshooting - Trouble Symptom Chart <automatic A/C>).

STEP 2. Connector check: C-105 engine-ECU connector

Q. Is the check result normal?

Go to Step 3 .

Repair or replace.

STEP 3. Check the trouble symptoms.

Q. Does trouble symptom persist?
Replace the engine-ECU. When the engine-ECU is replaced, write the chassis number (Refer to GROUP 00 - How to Perform Chassis Number Writing ). After replacing the engine-ECU, register the injector identification code and learn fuel injection (Refer to GROUP 00 - Precautions Before Service - What The Common Rail Engine Learns ).
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).